The big show Saturday night is the return of Speedy Ortiz, this time to Slowdown Jr. They’re opening for Tera Melos, a band that plays rough, angular math rock, very proggy, very syncopated, very dissonant, very good (if you’re into that sort of thing). The harsh rhythms are cut nicely by Nick Reinhart’s smooth vocals. From Sacramento. On Sargent House. Oquoa opens the evening at 9 p.m. $13 Adv./$15 DOS.